
/*
 * Copyright (c) 2020 - present, Inspur Genersoft Co., Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package io.iec.edp.caf.commons.configclient.bootstrap;

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

import org.springframework.context.EnvironmentAware;
import org.springframework.context.annotation.DeferredImportSelector;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.core.annotation.Order;
import org.springframework.core.env.Environment;
import org.springframework.core.io.support.SpringFactoriesLoader;
import org.springframework.core.style.ToStringCreator;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.util.StringUtils;

/**
 * This class uses {@link SpringFactoriesLoader} to load {@link BootstrapConfiguration}
 * entries from {@code spring.factories}. The classes are then loaded so they can be
 * sorted using {@link AnnotationAwareOrderComparator#sort(List)}. This class is a
 * {@link DeferredImportSelector} so {@code @Conditional} annotations on imported classes
 * are supported.
 *
 * @author Spencer Gibb
 */
public class BootstrapImportSelector implements EnvironmentAware, DeferredImportSelector {

    private Environment environment;

    private MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory();

    @Override
    public void setEnvironment(Environment environment) {
        this.environment = environment;
    }

    @Override
    public String[] selectImports(AnnotationMetadata annotationMetadata) {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        // Use names and ensure unique to protect against duplicates
        List<String> names = new ArrayList<>(
                SpringFactoriesLoader.loadFactoryNames(BootstrapConfiguration.class, classLoader));
        names.addAll(Arrays.asList(StringUtils
                .commaDelimitedListToStringArray(this.environment.getProperty("spring.cloud.bootstrap.sources", ""))));

        List<OrderedAnnotatedElement> elements = new ArrayList<>();
        for (String name : names) {
            try {
                elements.add(new OrderedAnnotatedElement(this.metadataReaderFactory, name));
            }
            catch (IOException e) {
                continue;
            }
        }
        AnnotationAwareOrderComparator.sort(elements);

        String[] classNames = elements.stream().map(e -> e.name).toArray(String[]::new);

        return classNames;
    }

    class OrderedAnnotatedElement implements AnnotatedElement {

        private final String name;

        private Order order = null;

        private Integer value;

        OrderedAnnotatedElement(MetadataReaderFactory metadataReaderFactory, String name) throws IOException {
            MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(name);
            AnnotationMetadata metadata = metadataReader.getAnnotationMetadata();
            Map<String, Object> attributes = metadata.getAnnotationAttributes(Order.class.getName());
            this.name = name;
            if (attributes != null && attributes.containsKey("value")) {
                this.value = (Integer) attributes.get("value");
                this.order = new Order() {
                    @Override
                    public Class<? extends Annotation> annotationType() {
                        return Order.class;
                    }

                    @Override
                    public int value() {
                        return OrderedAnnotatedElement.this.value;
                    }
                };
            }
        }

        @Override
        @SuppressWarnings("unchecked")
        public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
            if (annotationClass == Order.class) {
                return (T) this.order;
            }
            return null;
        }

        @Override
        public Annotation[] getAnnotations() {
            return this.order == null ? new Annotation[0] : new Annotation[] { this.order };
        }

        @Override
        public Annotation[] getDeclaredAnnotations() {
            return getAnnotations();
        }

        @Override
        public String toString() {
            return new ToStringCreator(this).append("name", this.name).append("value", this.value).toString();
        }

    }

}